Some types of implantable medical devices (IMDs), such as cardiac pacemakers or implantable cardioverter defibrillators (ICDs), provide therapeutic electrical stimulation to a heart of a patient via electrodes on one or more implantable endocardial or epicardial leads that are positioned in or adjacent to the heart. The therapeutic electrical stimulation may be delivered to the heart in the form of pulses or shocks for pacing, cardioversion or defibrillation. In some cases, an IMD may sense intrinsic depolarizations of the heart, and control the delivery of therapeutic stimulation to the heart based on the sensing.
Other types of IMDs include a leadless pacemaker, which may be used to sense electrical activity and/or deliver therapeutic signals to the heart. The leadless pacemaker may include one or more electrodes on its outer housing to deliver therapeutic electrical signals and/or sense intrinsic depolarizations of the heart. The leadless pacemaker may be positioned within or outside of the heart and, in some examples, may be anchored to a wall of the heart via a fixation mechanism.
Delivery of therapeutic electrical stimulation to the heart can be useful in addressing cardiac conditions such as ventricular dyssynchrony that may occur in patients. Ventricular dyssynchrony is a lack of synchrony or a difference in the timing of contractions in different ventricles of the heart. Significant differences in timing of contractions can reduce cardiac efficiency. Cardiac resynchronization therapy (CRT), delivered by an IMD to the heart, may enhance cardiac output by resynchronizing the electromechanical activity of the ventricles of the heart.
It is generally known that a greater number of patients may benefit from CRT but choose to forgo the therapy for a variety of reasons. For example, implanting an IMD involves a long procedure (˜1.5-2 hours) requiring skilled electrophysiologists (EPs), who are unavailable in some rural areas. Additionally, although post-implant complications are unlikely, issues can arise such as LV lead dislodgement, phrenic nerve stimulation, and pocket hematomas. Moreover, some patients are non-responsive to CRT which may be due to the location electrical stimulation is delivered. It is therefore desirable to develop new methods and systems for delivering CRT that reduces the likelihood of post-implant complications and may be able to deliver more effective CRT.